全文获取类型
收费全文 | 2759篇 |
免费 | 58篇 |
国内免费 | 39篇 |
专业分类
化学 | 1759篇 |
晶体学 | 15篇 |
力学 | 74篇 |
数学 | 338篇 |
物理学 | 670篇 |
出版年
2021年 | 27篇 |
2020年 | 23篇 |
2019年 | 19篇 |
2018年 | 16篇 |
2016年 | 34篇 |
2015年 | 31篇 |
2014年 | 40篇 |
2013年 | 106篇 |
2012年 | 100篇 |
2011年 | 130篇 |
2010年 | 83篇 |
2009年 | 56篇 |
2008年 | 122篇 |
2007年 | 149篇 |
2006年 | 125篇 |
2005年 | 114篇 |
2004年 | 111篇 |
2003年 | 104篇 |
2002年 | 106篇 |
2001年 | 79篇 |
2000年 | 74篇 |
1999年 | 57篇 |
1998年 | 41篇 |
1997年 | 44篇 |
1996年 | 51篇 |
1995年 | 38篇 |
1994年 | 48篇 |
1993年 | 46篇 |
1992年 | 47篇 |
1991年 | 29篇 |
1990年 | 42篇 |
1989年 | 41篇 |
1988年 | 26篇 |
1987年 | 21篇 |
1986年 | 25篇 |
1985年 | 50篇 |
1984年 | 37篇 |
1983年 | 25篇 |
1982年 | 39篇 |
1981年 | 30篇 |
1980年 | 41篇 |
1979年 | 35篇 |
1978年 | 46篇 |
1977年 | 37篇 |
1976年 | 33篇 |
1975年 | 31篇 |
1974年 | 19篇 |
1973年 | 39篇 |
1972年 | 15篇 |
1971年 | 15篇 |
排序方式: 共有2856条查询结果,搜索用时 0 毫秒
1.
2.
Benjamin J. K. Evans Susan M. Scott Antony C. Searle 《General Relativity and Gravitation》2002,34(10):1675-1684
We have developed a new tool for numerical work in General Relativity: GRworkbench. We discuss how GRworkbench's implementation of a numerically-amenable analogue to Differential Geometry facilitates the development of robust and chart-independent numerical algorithms. We consider, as an example, geodesic tracing on two charts covering the exterior Schwarzschild space-time. 相似文献
3.
Anthony B. Evans 《Designs, Codes and Cryptography》2006,40(1):121-130
In 1779 Euler proved that for every even n there exists a latin square of order n that has no orthogonal mate, and in 1944 Mann proved that for every n of the form 4k + 1, k ≥ 1, there exists a latin square of order n that has no orthogonal mate. Except for the two smallest cases, n = 3 and n = 7, it is not known whether a latin square of order n = 4k + 3 with no orthogonal mate exists or not. We complete the determination of all n for which there exists a mate-less latin square of order n by proving that, with the exception of n = 3, for all n = 4k + 3 there exists a latin square of order n with no orthogonal mate. We will also show how the methods used in this paper can be applied more generally by deriving several
earlier non-orthogonality results. 相似文献
4.
William Evans David Kirkpatrick 《Journal of Algorithms in Cognition, Informatics and Logic》2004,50(2):168-193
We consider the problem of restructuring an ordered binary tree T, preserving the in-order sequence of its nodes, so as to reduce its height to some target value h. Such a restructuring necessarily involves the downward displacement of some of the nodes of T. Our results, focusing both on the maximum displacement over all nodes and on the maximum displacement over leaves only, provide (i) an explicit tradeoff between the worst-case displacement and the height restriction (including a family of trees that exhibit the worst-case displacements) and (ii) efficient algorithms to achieve height-restricted restructuring while minimizing the maximum node displacement. 相似文献
5.
David M. Evans 《组合设计杂志》2004,12(6):459-465
For all ‘reasonable’ finite t, k, and s, we construct a t‐(?0, k, 1) design and a group of automorphisms which is transitive on blocks and has s orbits on points. In particular, there is a 2‐(?0, 4, 1) design with a block‐transitive group of automorphisms having two point orbits. This answers a question of P. J. Cameron and C. E. Praeger. The construction is presented in a purely combinatorial way, but is a by‐product of a new way of looking at a model‐theoretic construction of E. Hrushovski. © 2004 Wiley Periodicals, Inc. 相似文献
6.
7.
Alpeshkumar K. Malde Santosh A. Khedkar Evans C. Coutinho 《Journal of Physical Organic Chemistry》2007,20(2):151-160
Modification of peptides to produce peptidomimetics is of great interest, with the aim of designing potent, selective, and metabolically stable analogs having certain conformational properties. Organoboranes have been reported in the literature with a wide range of therapeutic applications. One of the therapeutically important class of molecules is amine‐carboxyboranes derived from amino acids by replacement of the Cα atom of an amino acid/peptide by boron. The conformational preferences of these peptides, with respect to backbone ω, ?, and ψ torsion angles, have been investigated by theoretical calculations. The amide bond in these molecules has the same geometry in the ground and transition states as the natural peptides. However, the boron isosteres of glycine and alanine peptides are less structured than their natural derivatives, but are distinguished by structures with a positive value for the ? angle, which is normally disfavored for natural peptides. This property could be used to build peptides with a geometry not usually seen in natural peptides. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
8.
9.
10.